Sound masking system with improved high-frequency spatial uniformity

ABSTRACT

Methods and apparatuses for addressing open space noise are disclosed. In one example, a system and method for masking open space noise includes outputting a noise masking sound from a plurality of balanced mode radiator loudspeakers distributed in a down-fire direction above an open space.

BACKGROUND OF THE INVENTION

Noise within an open space is problematic for people working within theopen space. Open space noise is typically described by workers asunpleasant and uncomfortable. Speech noise, printer noise, telephoneringer noise, and other distracting sounds increase discomfort. Thisdiscomfort can be measured using subjective questionnaires as well asobjective measures, such as cortisol levels.

For example, many office buildings utilize a large open office area inwhich many employees work in cubicles with low cubicle walls or atworkstations without any acoustical barriers. Open space noise, and inparticular speech noise, is the top complaint of office workers abouttheir offices. One reason for this is that speech enters readily intothe brain's working memory and is therefore highly distracting. Evenspeech at very low levels can be highly distracting when ambient noiselevels are low (as in the case of someone having a conversation in alibrary). Productivity losses due to speech noise have been shown inpeer-reviewed laboratory studies to be as high as 41%.

Another major issue with open offices relates to speech privacy. Workersin open offices often feel that their telephone calls or in-personconversations can be overheard. Speech privacy correlates directly tointelligibility. Lack of speech privacy creates measurable increases instress and dissatisfaction among workers.

In the prior art, noise-absorbing ceiling tiles, carpeting, screens, andfurniture have been used to decrease office noise levels. Reducing thenoise levels does not, however, directly solve the problems associatedwith the intelligibility of speech. Speech intelligibility can beunaffected, or even increased, by these noise reduction measures. Asoffice densification accelerates, problems caused by open space noisebecome accentuated.

As a result, improved methods and apparatuses for addressing open spacenoise are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements.

FIG. 1 illustrates a system for sound masking in one example.

FIG. 2 illustrates a simplified block diagram of the computing deviceshown in FIG. 1.

FIG. 3 is an illustration of a balanced mode radiator loudspeaker usedin the sound masking system shown in FIG. 1 in one example.

FIG. 4 is an illustration of a balanced mode radiator loudspeaker withenclosure in one example.

FIG. 5 illustrates placement of a plurality of balanced mode radiatorloudspeakers and microphones shown in FIG. 1 in a space in one example.

FIG. 6 illustrates placement of the balanced mode radiator loudspeakersand display device shown in FIG. 5 in one example.

FIG. 7 illustrates placement of the balanced mode radiator loudspeakersand display device shown in FIG. 5 in a further example.

FIG. 8 illustrates a water element system in one example.

FIG. 9 is a diagram illustrating a polar response of a balanced moderadiator loudspeaker in comparison to a pistonic speaker in one example.

FIG. 10 is a diagram illustrating a frequency response of a balancedmode radiator loudspeaker in comparison to a pistonic speaker in oneexample.

FIG. 11 illustrates a sound masking usage scenario in one example.

FIG. 12 is a flow diagram illustrating sound masking in one example.

FIG. 13A and FIG. 13B illustrate calculation of the linear dispersionfor the BMR speaker and dome speaker, respectively.

FIG. 13C is a sample graphic illustrates the relationship betweenconical dispersion and linear dispersion.

FIG. 14A illustrates calculation of the radius of coverage for the BMRspeaker.

FIG. 14B illustrates calculation of the radius of coverage for the domespeaker.

FIG. 14C illustrates the improved radius of coverage of the BMR speakerover the dome speaker.

FIG. 15 illustrates non-limiting examples of various coverage patterns.

FIG. 16A illustrates the obtained coverage pattern for the dome speakerand result of 64 required speakers.

FIG. 16B illustrates the obtained coverage for the BMR speaker andresult of 36 required speakers.

FIG. 16C illustrates a summary table of the data shown in FIGS. 16A and16B.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Methods and apparatuses for masking open space noise are disclosed. Thefollowing description is presented to enable any person skilled in theart to make and use the invention. Descriptions of specific embodimentsand applications are provided only as examples and various modificationswill be readily apparent to those skilled in the art. The generalprinciples defined herein may be applied to other embodiments andapplications without departing from the spirit and scope of theinvention. Thus, the present invention is to be accorded the widestscope encompassing numerous alternatives, modifications and equivalentsconsistent with the principles and features disclosed herein.

Block diagrams of example systems are illustrated and described forpurposes of explanation. The functionality that is described as beingperformed by a single system component may be performed by multiplecomponents. Similarly, a single component may be configured to performfunctionality that is described as being performed by multiplecomponents. For purpose of clarity, details relating to technicalmaterial that is known in the technical fields related to the inventionhave not been described in detail so as not to unnecessarily obscure thepresent invention. It is to be understood that various examples of theinvention, although different, are not necessarily mutually exclusive.Thus, a particular feature, characteristic, or structure described inone example embodiment may be included within other embodiments.

“Sound masking” (also referred to as “noise masking”) is theintroduction of sound or constant background noise (referred to hereinas “noise masking sound”) in a space in order to reduce speechintelligibility, increase speech privacy, and increase acousticalcomfort. For example, the introduced noise masking sound may be a natureassociated sound, such as flowing water or birdsong. For example, thenoise masking sound may be a pink noise, filtered pink noise, brownnoise, or other similar random noise (herein referred to simply as “pinknoise”) injected into the open office. Pink noise and nature associatedsounds are both effective in reducing speech intelligibility, increasingspeech privacy, and increasing acoustical comfort.

Sound masking systems may be one of two configurations, depending uponwhere and how the loudspeakers are placed and directed: (1) in-plenum,and (2) direct field. In-plenum configurations utilize speakersinstalled in the plenum (the area between the ceiling tiles and theceiling deck) oriented to produce a masking sound that is broadcastupwards toward the ceiling. The sound is directed upwards so that itreflects off of the ceiling deck and is returned back toward the groundthrough the ceiling tiles with increased diffusion. Creating a morediffuse sound decreases the ability of the worker to identify thelocation of the speakers, and reduces the creation of “hot” and “cold”spots, where the masking sound is loud or quiet enough to be highlynoticeable.

However, in relying on reflections off of the ceiling deck, in-plenumconfigurations suffer from several disadvantages. These disadvantagesinclude (1) increased power requirements to drive the loudspeakersbecause sound is directed in a direction opposite the worker open spaceand may be absorbed by the ceiling deck, (2) intervening structureswithin the plenum, such as HVAC ducts, absorb sound and causeun-predictable and non-uniform reflections (3) non-uniformity andunknowability of the ceiling deck material and resulting ability toreflect or absorb sound.

In contrast, direct field (herein also referred to as “down-fire”)configurations place the loudspeakers within the ceiling tiles or hungas pendants oriented to output sound downwards (i.e., down-fire) so thatthe speaker sound travels directly to the workers below. The inventorhas recognized that spatial uniformity is a critical problem which mustbe addressed to achieve optimal performance of down-fire sound maskingsystems. A primary goal of a sound masking system is to providesufficient spatial uniformity of audio such that a listener walkingthrough the space does not notice changes in the sound masking audiolevel and spectrum. As such, when used in sound masking systems,loudspeakers have different desired performance characteristics andrequirements than a typical entertainment application such as astationary user listening to music. The inventor has recognized andidentified key desired loudspeaker operational parameters as describedherein for sound masking applications when the listener is mobile withina series of distributed speakers.

Spatial uniformity is accomplished by spacing the loudspeakers in theceiling such that the coverage pattern from one loudspeaker atfrequencies of interest abuts or slightly overlaps the coverage patternfrom the adjacent loudspeakers at a listener's ear height. The inventorhas recognized that spatial uniformity of coverage at a listener's earheight due to a grid of distributed loudspeakers in a ceiling isdependent primarily upon the loudspeakers' directivity at frequencies ofinterest and the spacing between the speakers. Effective frequencies forreducing speech intelligibility via sound masking include thoseone-third octave frequency bands that contribute most to speechintelligibility (and thus are more important for masking speech),namely, and respectively, 2 kHz, 1.6 kHz, 2.5 kHz, 3.15 kHz, 1 kHz, and4 kHz. Low-frequency content in the sound masking audio is alsodesirable to create a more natural-sounding and acceptable sound field.

The inventor has also recognized that the use of conventional pistonicloudspeakers (e.g., cone loudspeakers or dome loudspeakers) in down-firesound masking applications poses several problems, including inherentundesirable performance characteristics which reduce theireffectiveness. Undesirably, conventional pistonic loudspeakers becomedirective as the emitted frequency is increased. “ka” is a dimensionlessproduct of the wavenumber k (2*pi/wavelength) and diaphragm radius a.When ka<0.5, the loudspeaker behaves like a point source(omnidirectional). When ka>3, the loudspeaker is considered highlydirectional. These conventional pistonic speakers suffer fromhigh-frequency beaming which yields a non-uniform spectrum when placedat conventional sound masking loudspeaker spacing, thereby diminishingspatial uniformity.

High-frequency “beaming” of conventional pistonic loudspeakersdistributed within a ceiling contributes to an imbalance of spatialuniformity at these higher frequencies, particularly when theloudspeakers are operating in a down-fire mode. This “beaming”emphasizes high-frequencies on-axis, which diminish more quickly thanlower (more omnidirectional) frequencies as one moves off-axis. Spatialuniformity at these higher frequencies is difficult to realize usingconventional pistonic loudspeakers in a down-fire configuration.

Achieving less directivity at high frequencies (and thus yielding moreuniform coverage in a sound masking system) is highly desirable butrequires that the pistonic loudspeaker diaphragm shrink considerably.Shrinking the diaphragm reduces low-frequency sensitivity as thediaphragm becomes physically less able to move air, which isundesirable. This phenomenon of increased directivity with risingfrequency (“beaming”) is the reason that many loudspeaker systemsincorporate a woofer, a tweeter, and a crossover circuit. These types ofloudspeaker systems are more complex and expensive. The inventor hasrecognized what is needed for distributed sound masking systems is aloudspeaker that exhibits both sufficient low-frequency output and lessdirective high-frequency output without requiring two separateloudspeakers in a single enclosure and a crossover.

The inventor has identified an improved sound masking system thatprovides enhanced spatial uniformity for a desired sound maskingspectrum is realized by utilizing loudspeakers which exhibit lessdirectivity at high frequencies while still maintaining practicallow-frequency sensitivity. In one embodiment, a balanced-mode radiator(BMR) is utilized to provide high-frequency (e.g., ≥2 kHz) spectraluniformity at a listener's ear height in a distributed down-fire soundmasking system. The BMR loudspeaker acoustically behaves more similarlyto ideal “point sources” than conventional pistonic loudspeakers. TheBMR loudspeaker employs modal radiation at higher frequencies, whichdoes not suffer from “beaming” found in conventional pistonicloudspeakers.

Advantageously, the sound masking system with distributed BMRloudspeakers provides wider high-frequency dispersion, greaterlow-frequency sensitivity, and much greater mid-range sensitivity in adown-fire sound masking system. As such, a distributed sound maskingsystem utilizing down-fire BMR loudspeakers implemented within a ceilingplane provide better spatial uniformity with regards to frequencies thatare effective at masking speech than prior art systems. Furthermore,unlike conventional pistonic speakers, BMR loudspeakers maintainexcellent high frequency dispersion at increased diameter sizes, therebyallowing systems to use larger speakers which offer both excellent highfrequency dispersion and better lower frequency response.

The described methods and systems offer several advantages. Thedistributed sound masking system utilizing down-fire BMR loudspeakersprovides (1) wider high-frequency dispersion which allows for betterspatial uniformity at frequencies most important for masking speech, (2)wider high-frequency dispersion which enhances the subjective realism ofnon-traditional masking sounds, such as recordings of running water(e.g., streams, creeks, rivers), and other nature sounds, (3) reducedoverall system costs of goods sold because BMR loudspeakers arefull-range loudspeakers that obviate the need for a tweeter, woofer, andcrossover circuit, and (4) higher mid-frequency sensitivity (1 kHz)means that less power is required to achieve the same sound pressurelevel.

In one example embodiment of the invention, a method for masking openspace noise includes outputting a noise masking sound from a pluralityof balanced mode radiator loudspeakers distributed in a down-firedirection above an open space. In one example, the method furtherincludes displaying a visual corresponding to the noise masking sound.

In one example embodiment, a system for masking open space noiseincludes a plurality of balanced mode radiator loudspeakers, eachbalanced mode radiator loudspeaker arranged above an open space in adown-fire configuration to output a speaker sound downward into the openspace. Each balanced mode radiator loudspeaker includes a voice coil, adiaphragm, and one or more mass objects coupled to the diaphragm. Thesystem includes a display device disposed in the open space.

The system further includes one or more computing devices including oneor more processors and one or more memories. The one or more memoriesstore one or more selectable noise masking sound audio files and one ormore selectable video files. The one or more memories further store oneor more application programs executable by the one or more processorsconfigured to output a noise masking sound audio file selected from theone or more selectable noise masking sound audio files at the pluralityof balanced mode radiator loudspeakers and output a video file selectedfrom the one or more selectable video files at the display device.

In one example embodiment, a system for masking open space noiseincludes a plurality of balanced mode radiator loudspeakers arrangedabove an open space to output a noise masking sound in a down-firedirection. Each balanced mode radiator loudspeaker of the plurality ofbalanced mode radiator loudspeakers comprising a voice coil, adiaphragm, and one or more mass objects coupled to the diaphragm. Thesystem includes a plurality of microphones. The system further includesone or more computing devices including one or more processors and oneor more memories storing one or more application programs executable bythe one or more processors. The one or more application programs includeinstructions to receive a microphone data from at least one of theplurality of microphones and adjust the noise masking sound output atone or more of the plurality of balanced mode radiator loudspeakers.

FIG. 1 illustrates a system 2 for sound masking in one example. Thesound masking may include, for example, outputting noise masking sounds.System 2 includes a computing device 4, BMR loudspeakers 14 arranged tooutput a speaker sound in an open space, microphones 15, and videodisplay 16 disposed in the open space. Computing device 4 may forexample be a laptop, tablet computer, desktop personal computer, server,or smartphone. Computing device 4 stores selectable noise masking soundaudio files 10 and selectable video files 12. Computing device 4 furtherstores a noise management application 6 configured to receive a userselection or automatically select a noise masking sound audio file fromthe selectable noise masking sound audio files 10 and a video file fromthe selectable video files 12. Noise management application 6 includesor interfaces with a digital audio player and a digital video player atcomputing device 4. Noise management application 6 outputs (i.e., plays)the selected noise masking sound audio file at BMR loudspeakers 14 andoutputs (i.e., plays) the selected video file at video display 16.Although only a single video display 16 is shown, multiple displays maybe utilized to output the selected video file.

In one example embodiment, noise management application 6 interfaceswith microphones 15 to receive microphone data 17. The microphone data17 may be any data which can be derived from processing sound detectedat a microphone. For example, the microphone data 17 may include noiselevel measurements, frequency distribution data, or voice activitydetection data determined from sound detected at the one or moremicrophones 15. Furthermore, in addition to or in alternative to, themicrophone data 17 may include the sound itself (e.g., a stream ofdigital audio data).

Balanced mode radiator loudspeakers 14 are disposed above an open spaceand arranged to direct the speaker sound in a down-fire directiondirectly into the open space. In one example, BMR loudspeakers 14 are aplurality of speakers disposed at varying distances from the videodisplay 16. An output level of the speaker sound from a speaker may beadjusted based on the distance of the speaker from the video display 16.In one example, video display 16 may be visible from any location withinthe open space.

In one example, a server 20 is capable of communications with computingdevice 4 via one or more communication network(s) 18 utilizing wired orwireless network connections. For example, communication network(s) 18may include an Internet Protocol (IP) network, cellular communicationsnetwork, public switched telephone network, IEEE 802.11 wirelessnetwork, Bluetooth network, or any combination thereof.

Server 20 includes a sound masking application 25 and stores noisemasking audio files 22 and video files 24. In one example, the soundmasking application 25 is configured to transmit one or more of noisemasking audio files 22 and video files 24 to computing device 4 uponrequest by noise management application 6 at computing device 4. In oneexample, noise masking audio files 22 and video files 24 are stored indata structure 8. In a further example, noise masking audio files 22 andvideo files 24 are streamed to noise management application 6 for directoutput to BMR loudspeakers 14 and display(s) 16, respectively.

FIG. 2 illustrates a simplified block diagram of the computing device 4shown in FIG. 1 capable of performing sound masking and outputtingselected associated visuals. The computing device 4 includes a processor26 operably coupled via an interconnect 38 to a data communicationsinterface 28, memory 30, a microphone 32, a speaker 34, and a userinterface 36. In one example, data communications interface 28 is awireless communications transceiver (e.g., utilizing IEEE 802.11communications) operable to receive or identify location data fromcommunication network(s) 18.

Memory 30 stores a data structure 8 (e.g., a database, table, or anyother file/memory structure) for storing sound masking data, includingnoise masking audio files 10, video files 12, and microphone data 17.Memory also stores noise management application 6 configured andoperating as described herein. Memory 30 may include a variety ofmemories, and in one example includes SDRAM, ROM, flash memory, or acombination thereof. Memory 30 may further include separate memorystructures or a single integrated memory structure. In one example,memory 30 may be used to store passwords, network and telecommunicationsprograms, and/or an operating system (OS).

Processor 26, using executable code and applications stored in memory,performs the necessary functions associated with managing the noisemasking and audio files and associated visuals within an environmentsuch as a building open space as described herein. In one example,processor 26 further interacts with server 20 to receive noise maskingaudio files 22 and video files 24. In one example, processor 26 is ahigh performance, highly integrated, and highly flexible system-on-chip(SoC), including signal processing functionality. Processor 26 mayinclude a variety of processors (e.g., digital signal processors), withconventional CPUs being applicable. User interface 36 allows for manualcommunication between the system user (e.g., a system administrator) andthe computing device 4, and in one example includes an interfaceallowing the system user to manually input a current location of thebuilding in which the system 2 is being used.

In one example operation, a system user selects from the noise maskingsound audio files 10 and video files 12. The selected noise maskingsound audio file is output to a BMR loudspeaker 14 and the selectedvideo file is output to a video display 16.

In a further example operation, a location data is received oridentified at computing device 4 (e.g., the sound masking system). Inone example, the location data is an Internet Protocol address and theuser location is determined from the Internet Protocol address. In oneexample, the location data includes a city, state, or region data.Computing device 4 may, for example, receive or identify itsgeo-location utilizing an IP address, Wi-Fi connection data, or GlobalPositioning System (GPS) data. A noise masking sound audio file isselected from the selectable noise masking sound audio files 10 and avideo file from the selectable video files 12 utilizing the locationdata. The selected noise masking sound audio file is output to a BMRloudspeaker 14 and the selected video file is output to a video display16. In one example, the selectable noise masking sound audio files 10and the selectable video files 12 are correlated to a plurality oflocations in a data structure. In further examples, other parameters areutilized to select the sound audio file 10 and video file 10, includinga current time of day or current weather condition.

In one example, the noise masking sound audio file 10 includes a natureassociated sound and the video file 12 includes a nature associatedvisual. For example: (1) the nature associated sound includes a watersound and the nature associated visual includes a water visual, (2) thenature associated sound includes a beach sound and the nature associatedvisual includes a beach visual, or (3) the nature associated soundincludes a forest sound and the nature associated visual includes aforest visual. In one example, the video file selected and the noisemasking sound audio file selected are associated (e.g., selecting aparticular noise masking sound audio file automatically selects aparticular video file and vice versa) at the sound masking system.

In one example configuration and operation, noise management application6 is configured to receive a microphone data 17 from at least one of theplurality of microphones 15 and adjust the sound masking sound output(e.g., adjusts a volume level of the noise masking sound) at one or moreof the plurality of BMR loudspeakers 14. For example, microphone data 17includes noise level measurements, noise frequency data, or voiceactivity detection data determined from sound detected at the pluralityof microphones 15. In one example, noise management application 6selects a noise masking sound audio file from the selectable noisemasking sound audio files 10 and the video file from the selectablevideo files 12 utilizing the a microphone output data from the pluralityof microphones 15.

FIG. 3 is an illustration of a BMR loudspeaker 14 in one example. Asillustrated in FIG. 3, BMR loudspeaker 14 is an assembly oriented in adown-fire configuration to emit sound in downward direction 60 (alsoshown in FIGS. 6 and 7). BMR loudspeaker 14 employs a flat diaphragm(i.e., panel) 40 attached to a voice coil 46, a magnet 52, magnet 54,U-yoke 56, and damper 58. BMR loudspeaker 14 includes surround 48attached to the rear of the diaphragm 40. BMR loudspeaker 14 includesbalancing masses 42, 44 attached to the rear of the diaphragm 40.Balancing masses 42, 44 restore the acoustical behavior of a “free disc”and are placed to the left and right of the voice coil 46 atpre-determined diameters. The location of the balancing masses 42, 44(and voice coil 46) is determined by evaluating the diaphragm 40'smechanical admittance at radial positions varying from the center to theedge of the diaphragm 40 and determining its average over all modes inthe frequency range of interest. The values of the masses are scaled bythe relative ratios of diameters. Flat diaphragm 40 is selected to havea stiffness such that the first bending mode is located in the frequencyrange where the diaphragm would otherwise start to beam sound. Thesurround 49 is selected to have a weight, damping, and diameter toachieve good control for all bending modes.

BMR loudspeaker 14 attempts to achieve the acoustic response of a “freedisc”, as opposed to the acoustic response of a “piston in an infinitebaffle” which has the well-known “ka dilemma” of increasing directivity(lobing or beaming) with increasing frequency or decreasing diaphragmsize. This is done by exploiting the modal behavior of the diaphragm 40and designing a limited number of evenly spread modes to radiatepurposefully in the frequency region where pistonic motion begins tobecome directive. In one example, BMR loudspeaker 14 is one such as thatis available from Tectonic Elements Ltd, United Kingdom.

FIG. 4 is an illustration of a balanced mode radiator loudspeakerhousing 70 containing a BMR loudspeaker 14 in one example. Loudspeakerhousing 70 includes tuned bass reflex port(s) 72, 74 allowing air tocirculate within housing 70 and resonate at a lower frequency than theloudspeaker, thereby improving low frequency response.

FIG. 5 illustrates placement of a plurality of BMR loudspeakers 14 andmicrophones 15 shown in FIG. 1 in a space 400 in one example.Microphones 15 may be arranged in a ceiling area to detect sound in thespace 400.

Use of BMR loudspeakers 14 instead of conventional pistonic loudspeakershas previously unrecognized and unexpected advantages in systems to maskopen space noise. With the same loudspeaker spacing (i.e., the samenumber of BMR loudspeakers for a given space) within a ceiling grid, theresultant sound field is richer and more detailed, which is due to thewider dispersion at higher frequencies. Sound quality is improved withbetter spatial uniformity of high frequencies than pistonicloudspeakers. Alternatively, at a slightly wider spacing (i.e., a fewernumber of BMR loudspeakers for a given space size), the BMR loudspeakerscan provide a similar sound field as that provided by pistonicloudspeakers using less loudspeakers, saving on cost and installation.In one example described in further detail below, in a space with anarea of 10000 sq. ft., a ceiling height of 10 ft., and a listener heightof 4 ft., 36 BMR speakers provide the same coverage (at 2 kHz) as 64pistonic loudspeakers, a 44% reduction in the number of requiredspeakers.

Undesirable high-frequency beaming that occurs with conventionalpistonic loudspeakers is very apparent in a down-fire configuration;listeners in the open space 400 below hear these frequencies as verypronounced when directly underneath the loudspeaker (on-axis). This isespecially audible as a person moves throughout the open space and isdetrimental to spatial uniformity. As the BMR loudspeakers 14 do notbeam as much, higher frequencies are less pronounced on-axis,contributing to better high-frequency spatial uniformity within the openspace.

Illustrated in FIG. 5, there is one BMR loudspeaker 14 for eachmicrophone 15 located in a same geographic sub-unit. In furtherexamples, the ratio of BMR loudspeakers 14 to microphones 15 may bevaried. In one example configuration, each microphone of the pluralityof microphones 15 is associated with a BMR loudspeaker of the pluralityof BMR loudspeakers 14. For example, each microphone of the plurality ofmicrophones 15 is correlated based on geographic location to acorresponding BMR loudspeaker of the plurality of BMR loudspeakers 14.In one example, each microphone 15 location and BMR loudspeaker 14location within open space 400, and a correlated microphone 15 andloudspeaker 14 pair located within the same sub-unit, is recorded duringan installation process of the system 2.

The plurality of BMR loudspeakers 14 and video display 16 are undercontrol of the computing device 4. In one example, computing device 4interfaces with server 20 to receive audio data and video data.Placement of a plurality of the BMR loudspeakers 14 and video display 16in a space 400 is shown in one example. For example, space 400 may be anopen space such as a large room of an office building. The video display16 is arranged to be easily visible within the open space. For example,video display 16 is a direct lit led array display, projected image ontoa wall mounted screen, or a flat panel LCD.

Computing device 4 performs operations as described herein to outputsound masking signals and video signals. Computing device 4 is capableof electronic communications with each BMR loudspeaker 14, microphone15, and display 16 via either a wired or wireless communications link.For example, computing device 4, BMR loudspeakers 14, microphones 15,and display 16 are connected via one or more communications networkssuch as a local area network (LAN) or an Internet Protocol network.

In one example, each BMR loudspeaker 14, microphone 15, and display 16is network addressable and has a unique Internet Protocol address forindividual control. BMR loudspeaker 14 includes a processor operablycoupled to a network interface, output transducer, memory, amplifier,and power source. BMR loudspeaker 14 also includes a near-field wirelessinterface utilized to link with a control device such as computingdevice 4. In one example, the network interface is a wirelesstransceiver and accompanying antenna for communications with a wirelessrouter or access point. For example, the wireless transceiver is aBluetooth or IEEE 802.11 transceiver. In a further example, the networkinterface is a wired interface, such as that an Ethernet jack used toconnect to computing device 4 over the Internet or a local area network.The processor allows for processing data, including managing soundmasking signals over the network interface, and may include a variety ofprocessors (e.g., digital signal processors), with conventional CPUsbeing applicable. Similarly, display 16 also includes a processoroperably coupled to a network interface, wireless interface, outputtransducer, memory, amplifier, and power source.

In the system illustrated in FIG. 5, sound is output from BMRloudspeakers 14 corresponding to a sound masking signal configured tomask open space noise. In one example, the sound masking signal is arandom noise such as pink noise. The sound operates to mask open spacenoise heard by a person in open space 400. In one example, the maskinglevels are advantageously dynamically adjusted in response to noiselevel measurements made in the open space 400. In one example, maskinglevels are adjusted on a speaker-by-speaker basis in order to addresslocation-specific noise levels.

In one example, the speaker sound is the sound of a flow of water. Inone example, the sound corresponding to the flow of water is a recordingof a natural flow of water or an electronically synthesized sound offlow of water. In one example, the sound corresponding to a flow ofwater has been optimized to mask open space noise. For example, arecording of the flow of water has been processed to add 2-4 dB peroctave higher frequency boost.

In one example, the BMR loudspeaker 14 is one of a plurality of speakersdisposed at varying distances from the video display 16, where an outputlevel of the speaker sound from a speaker is adjusted based on thedistance of the BMR loudspeaker 14 from the video display 16. Thespeaker output level is adjusted so that the sound level of the flowingwater (the sound from a speaker at video display 16 combined with thesound of flowing water output from BMR loudspeaker 14) is consistentthroughout the open space.

In one example, based on measured noise levels, sound masking system 2makes changes to the physical environment, including (1) increasing orreducing the volume of the sound masking in order to maintain an optimalmasking level, even as speech noise levels change, (2) modifying themasking sound source and/or type—for example, from a sound of birdschirping to a sound of a waterfall, or (3) modifying the masking soundspectrum—for example, from a filtered pink noise to a noise that iscloser to brown noise—in response to volume or noise densityinformation, or (4) increasing or decreasing the lighting level, or tochanging the color of ambient lighting in open space 400. In oneexample, sound masking system 2 modifies the visual displayed on videodisplay 16 responsive to a change in the sound environment (i.e., wherethe sound audio file 10 is changed, the video file 12 is changed).

FIG. 6 illustrates placement of the BMR loudspeakers 14 and videodisplay 16 shown in FIG. 5 in one example. FIG. 6 illustrates placementof the BMR loudspeakers 14 in a down-fire (i.e., direct field)configuration, whereby the speakers 14 are oriented to direct sounddownwards. The masking sound travels directly from the speakers to alistener without interacting with any reflecting or transmittingfeature.

In one example, the BMR loudspeakers 14 are disposed at a desiredvariable height above an open space floor. The total number of BMRloudspeakers 14 within the open space may be adjusted based on thedesired variable height above the open space floor. In one example, thedesired variable height is determined by a wire cable 602 or pole havinga first end coupled to the ceiling and a second end coupled to a BMRloudspeaker. Advantageously, the number of BMR loudspeakers 14 requiredfor a given sized open space can be adjusted by adjusting this variableheight. As the length of wire cable 602 is shortened, the number of BMRloudspeakers 14 is reduced.

In one example, system 2 receives a desired variable height above anopen space floor for a BMR loudspeaker 14. For example, the desiredvariable height may be input by a user. System 2 determines a totalnumber of BMR loudspeakers 14 within the open space utilizing thedesired variable height above the open space floor.

FIG. 7 illustrates placement of the BMR loudspeakers 14 and videodisplay 16 shown in FIG. 5 in a further example. FIG. 7 illustratesplacement of the BMR loudspeakers 14 in a direct field configuration,whereby the speakers are oriented to direct sound downwards. In thisexample, space 400 includes ceiling tiles below a ceiling deck, with aplenum area disposed there between. BMR loudspeakers 14 are disposed atthe fixed height of the ceiling tiles so that the BMR loudspeakers 14are flush with the ceiling tiles, whereby the ceiling tiles includesound apertures. The masking sound travels directly from the speakers toa listener without interacting with any reflecting or transmittingfeature.

FIG. 8 illustrates a water element system 800 in one example. In oneembodiment, system 2 further includes a water element system 800 (i.e.,a physical display of moving water) in the open space in addition tovideo display 16. In a further embodiment, water element system 800 isused in place of video display 16. The water element system 800 isarranged to be easily visible within the open space. Water sound fromwater element system 800 also operates to mask open space noise 620. Theintelligibility of speech and other noise within space 400 is reduced bythe sound from water element system 800. In one example, the waterelement system 800 is a floor-to-ceiling waterfall including an upperreservoir which receives water from a water supply, and a lowerreservoir (e.g., a floor basin) to receive water which has fallen fromthe upper reservoir.

The waterfall includes water recirculation tubes for recirculating waterfrom the lower reservoir back to the upper reservoir, and arecirculation pump to recirculate the water through the recirculationtubes up to the upper reservoir. In one implementation, water falls fromupper reservoir to the lower reservoir along the surfaces of one or morevertical glass panels disposed between the upper reservoir and the lowerreservoir. The flow rate and water volume of the waterfall may beadjusted to control the water sound level.

In one example, each BMR loudspeaker 14 is one of a plurality ofspeakers disposed at varying distances from the water element system800, where an output level of the speaker sound from a speaker isadjusted based on the distance of the BMR loudspeaker 14 from the waterelement system 800. The speaker output level is adjusted so that thesound level of the flowing water (i.e., the sound from the water elementsystem 800 combined with the sound of flowing water output from BMRloudspeaker 14) is consistent throughout the open space. At locations inclose proximity to water element system 800, water sound from the waterelement system 800 is heard. As such, the output level of a BMRloudspeaker 14 in close proximity to water element system 800 is reducedrelative to a BMR loudspeaker 14 further away. In one example, thespeaker sound has been processed to match the frequency characteristicsof the water sound emanating from water element system 800 so that theuser is under the impression that the speaker sound is emanating fromwater element system 800 instead of BMR loudspeaker 14.

In this manner, the water element system 800 may be constructed so thatit need not be so loud so as to be heard throughout the open space inorder for the water sound to be an effective noise masker. This reducesthe possibility that workers in close proximity to the water elementsystem 800 will find the water sound too loud and annoying whileallowing workers further away to hear water sound at a sufficient levelto provide effective masking of the open space noise.

FIG. 9 is a diagram illustrating a polar response of a BMR loudspeaker14 in comparison to a pistonic speaker in one example. Illustrated isthe polar response 902 at 2 kHz of a 60-mm BMR loudspeaker 14 in aported enclosure and the polar response 904 of a 31-mm dome (i.e.,pistonic) loudspeaker in a ported enclosure. The BMR loudspeaker 14exhibits wider dispersion at this 2 kHz frequency which contributes mostto masking speech. As illustrated, for any rotation off-axis (e.g., 320degrees), polar response 902 of BMR loudspeaker 14 shows less loss(i.e., less decrease in gain) relative to polar response 904 of the domeloudspeaker. BMR loudspeakers 14 of varying sizes were tested. BMRloudspeakers 14 having larger diameters continued to provide excellentand improved high frequency dispersion relative to the pistonic speaker.

FIG. 10 is a diagram illustrating a frequency response of a BMRloudspeaker 14 in comparison to a pistonic speaker in one example.Illustrated is the frequency response 1002 of a 60-mm BMR loudspeaker 14in a ported enclosure and the frequency response 1004 of a 31-mm domeloudspeaker in a ported enclosure. As shown, BMR loudspeaker 14 exhibitsprovides better low-frequency sensitivity and much greater mid-frequencysensitivity than the dome loudspeaker. As such, BMR loudspeaker 14provides superior performance in outputting both nature sounds incombination with random pink or white noise. Advantageously, utilizingBMR loudspeakers 14, one or more noise masking sound audio file 10 mayinclude a random noise (e.g., pink or white noise) including a frequencyrange of 160-8000 Hz and a natural sound (e.g., water sound or forestsound such as birds or crickets) including a frequency range of120-10000 Hz.

FIG. 11 illustrates a sound masking usage scenario in one example. Aconversation participant 1112 is in conversation with a conversationparticipant 1114 in the vicinity of person 1110 in an open space. Openspace noise 1120 includes components of speech 1116 from participant1112 and speech 1118 from conversation participant 1114.

Sound 1104 output from BMR speaker 14 operates to mask open space noise1120 heard by a person 1110. Sound 1104 corresponds to output of a noisemasking audio file 10 selected by noise management application 6. Visual1124 is shown on video display 16. Visual 1124 corresponds to output ofa video file 12 selected by noise management application 6. Videodisplay 16 may also include a speaker which outputs sound 1108 matchingsound 1104. Sound 1108 from display 16 also operates to mask open spacenoise 1120. The intelligibility of speech 1116 and speech 1118 isreduced by sound 1104 and sound 1108.

In one example, sound 1104 is a sound of flowing water, such as that ofa waterfall or flowing stream. Visual 1124 is selected to correspond tosound 1104 or be compatible with sound 1104. If sound 1104 is a sound offlowing water, visual 1124 is an image of flowing water, such as that ofan image of a waterfall or a flowing stream. The presence of visual 1124shown on video display 16 advantageously increases the user comfort whenlistening to water sound 1104 output from BMR loudspeaker 14 as theperson 1110 has a frame of reference as to the source of the water sound1104. Playing water sounds alone through the sound masking BMRloudspeaker 14, without a visual water element, causes discomfort amongworkers, who feel as though the water is dripping down from the ceilingor that it has no logical source. A logical source of the water sound isneeded.

In one example, the noise masking audio file 10 played to generate sound1104 is a recording of a natural sound or an electronically synthesizedsound. In one example, the sound 1104 has been optimized to mask openspace noise. For example, a recording of a natural sound has beenprocessed to add 2-4 dB per octave higher frequency boost.

In the scenario illustrated in FIG. 11, a sound 1122 is output from BMRloudspeaker 14 corresponding to a noise configured to mask open spacenoise in addition to the sound 1104. For example, where sound 1104 is awater sound, sound 1122 may be a random noise such as pink noise. Forexample, sound 1122 is generated from the same or a different noisemasking audio file as sound 1104. Both sound 1104 and sound 1122 operateto mask open space noise 1120 heard by person 1110.

In one example, the speaker sound 1104 corresponding to the flow ofwater is optimized to mask a higher frequency open space noise than thenoise sound 1122 configured to mask open space noise. For example, afrequency boost of 2-4 dB per octave is added in the processing of therecorded water sound. In this manner, noise sound 1122 can be selectedto mask lower frequency open space noise. For example, noise sound 1122can be selected to be a pink noise which is more appealing to be heardby persons instead of a white noise, which is slightly more effective inmasking higher frequency open space noise but more unpleasant forpersons to hear.

In one example, a method for masking open space noise (e.g., noise 1120)includes outputting a first masking sound (e.g., sound 1122, such as apink noise) to mask an open space noise (e.g., noise 1120) in an openspace, and masking the audibility of the first masking sound (e.g.,sound 1122) utilizing a second masking sound (e.g., sound 1104), thesecond masking sound (e.g., sound 1104) also operable to mask the openspace noise (e.g., noise 1120). This methodology allows the level of thefirst masking sound (e.g., sound 1122) to be increased (i.e., to producea greater masking effect of noise 1120) without being perceived byperson 1110. This is advantageous where persons prefer to hear the soundof pink noise at a reduced level or not to hear the sound of pink noise.In one example, the output levels of sound 1104 and noise sound 1122 aredetermined experimentally and/or based on listener preference. The useof sound 1104 and sound 1122 produces a greater masking effect than theuse of either sound 1104 or sound 1122 alone, while providing forincreased listener comfort.

FIG. 12 is a flow diagram illustrating sound masking in one example. Forexample, the process illustrated may be implemented by the system shownin FIG. 1. At block 1202, a noise masking sound is output from aplurality of BMR loudspeakers distributed in a down-fire direction abovean open space. In one example, the noise masking sound output includes arandom noise (e.g., pink or white noise) including a frequency range of160-8000 Hz and a natural sound (e.g., water sound or forest sound)including a frequency range of 120-10000 Hz.

In one example, the plurality of BMR loudspeakers are disposed at adesired variable height above an open space floor. For example, thedesired variable height is determined by an extension segment having afirst end coupled to a ceiling and a second end coupled to a BMRloudspeaker. In one example, the total number of BMR loudspeakers withinthe open space is adjusted based on the desired variable height abovethe open space floor.

At block 1204, a visual corresponding to the noise masking sound isdisplayed. In one example, displaying the visual corresponding to thenoise masking sound includes displaying a nature visual on a videodisplay device. In one example, the noise masking sound includes a watersound and displaying the visual corresponding to the noise masking soundincludes displaying a water element system, the water element systemgenerating a sound of flowing water. For example, the water elementsystem generating the sound of flowing water includes a floor-to-ceilingwaterfall.

In one example, the noise masking sound includes a nature associatedsound and the visual includes a nature associated visual. For example,(1) the nature associated sound includes a water sound and the natureassociated visual includes a water visual, (2) the nature associatedsound includes a beach sound and the nature associated visual includes abeach visual, or (3) the nature associated sound includes a forest soundand the nature associated visual includes a forest visual.

In one example, the process further includes receiving a desiredvariable height above an open space floor for each BMR loudspeaker. Atotal number of BMR loudspeakers within the open space is determinedutilizing the desired variable height above the open space floor.

In one example, the process further includes receiving a microphone datafrom a plurality of microphones disposed in the open space. The noisemasking sound is adjusted utilizing the microphone data. For example,the sound masking volume level, masking type, or frequency is adjusted.Each microphone of the plurality of microphones may be associated with aBMR loudspeaker.

EXAMPLE

In one example, the number of BMR loudspeakers to provide a similarsound field quality required for a given space size is reduced by 44%.Determination of the number of loudspeakers for a given space size inone example, and resulting improvement using BMR speakers, is shown inFIGS. 9 and 13A-16C. In this example, comparison between a 60 mm BMRspeaker and 30 mm dome speaker is illustrated for a room size of 10,000square feet, ceiling height of 10 feet, listener height of 4 feet, andcoverage pattern of edge-to-edge.

First, the linear dispersion of each speaker is calculated, as shown inFIGS. 9 and 13A-13C. To obtain the linear dispersion, first the conicaldispersion of each loudspeaker is measured in an anechoic chamber toobtain polar plots, indicating off-axis degradation. Conical dispersionis the angle at which the response falls by −6 dB. In this example,analysis was done for 2-kHz, which is of primary interest in masking ofspeech intelligibility; designing for coverage at 2-kHz is fairlystandard for AV industry. FIG. 9 illustrates the obtained polar plots.

FIG. 13A and FIG. 13B illustrate calculation of the linear dispersionfor the BMR speaker and dome speaker, respectively. At 5-degreeincrements, known and relative attenuation due to distance are added.Wider angles need to travel farther to reach the listening plane, set inthis example at 4-ft. above the floor. Losses due to dispersion (fromthe polar plots) are combined with attenuation due to distance foroverall attenuation at the listening plane. The angle at which thecombined loss due to dispersion and attenuation due to distance is −6 dBis known as the linear dispersion and is used for calculating coverage.Due to slight asymmetry in the polar plots, the right and left-handsides are averaged to determine linear dispersion angle. Lineardispersion is always narrower than conical dispersion. FIG. 13C is asample graphic illustrates the relationship between conical dispersionand linear dispersion.

After the linear dispersion of both the BMR speaker and the dome speakeris obtained, it is utilized in calculating the “radius of coverage” foreach speaker. FIG. 14A illustrates calculation of the radius of coveragefor the BMR speaker. FIG. 14B illustrates calculation of the radius ofcoverage for the dome speaker. FIG. 14C illustrates the improved radiusof coverage of the BMR speaker over the dome speaker.

Next, a circle with radius equal to the radius of coverage is overlaidon an architectural floor plan or reflected ceiling plan. In thisexample, a generic, symmetric square space is used for ease ofcomparison. A coverage pattern based on desired overlap is selected.Selection may be based, for example, on program goals or userpreference. In this example, an “edge-to-edge” coverage is selectedwhere the radius of coverage from one speaker abuts but does not overlapwith the radius of coverage from another speaker. FIG. 15 illustratesnon-limiting examples of various coverage patterns which may be used.Coverage circles with appropriate spacing to cover the space (e.g.,utilizing an “edge-to-edge” coverage pattern) are added, producing therequired number of loudspeakers. This process is repeated for both theBMR speaker and the dome speaker to provide the desired comparison ofthe number of BMR speakers relative to the number of dome speakers. FIG.16A illustrates the obtained coverage pattern for the dome speaker andresult of 64 required speakers. FIG. 16B illustrates the obtainedcoverage for the BMR speaker and result of 36 required speakers, a 44%reduction in the number of required speakers to obtain a similar soundfield quality. FIG. 16C illustrates a summary table of the data shown inFIGS. 16A and 16B.

While the exemplary embodiments of the present invention are describedand illustrated herein, it will be appreciated that they are merelyillustrative and that modifications can be made to these embodimentswithout departing from the spirit and scope of the invention. Actsdescribed herein may be computer readable and executable instructionsthat can be implemented by one or more processors and stored on acomputer readable memory or articles. The computer readable andexecutable instructions may include, for example, application programs,program modules, routines and subroutines, a thread of execution, andthe like. In some instances, not all acts may be required to beimplemented in a methodology described herein.

Terms such as “component”, “module”, and “system” are intended toencompass software, hardware, or a combination of software and hardware.For example, a system or component may be a process, a process executingon a processor, or a processor. Furthermore, a functionality, componentor system may be localized on a single device or distributed acrossseveral devices. The described subject matter may be implemented as anapparatus, a method, or article of manufacture using standardprogramming or engineering techniques to produce software, firmware,hardware, or any combination thereof to control one or more computingdevices.

Thus, the scope of the invention is intended to be defined only in termsof the following claims as may be amended, with each claim beingexpressly incorporated into this Description of Specific Embodiments asan embodiment of the invention.

What is claimed is:
 1. A system for masking open space noise comprising:a plurality of balanced mode radiator loudspeakers, each balanced moderadiator loudspeaker arranged above an open space in a down-fireconfiguration to output a speaker sound downward into the open space,and each balanced mode radiator loudspeaker comprising a voice coil, adiaphragm, and one or more mass objects coupled to the diaphragm; adisplay device disposed in the open space; and one or more computingdevices comprising: one or more processors; one or more memoriesstoring: one or more selectable noise masking sound audio files and oneor more selectable video files; and one or more application programsexecutable by the one or more processors configured to output a noisemasking sound audio file selected from the one or more selectable noisemasking sound audio files at the plurality of balanced mode radiatorloudspeakers and output a video file selected from the one or moreselectable video files at the display device.
 2. The system of claim 1,wherein the plurality of balanced mode radiator loudspeakers aredisposed at a desired variable height above an open space floor.
 3. Thesystem of claim 2, wherein a total number of balanced mode radiatorloudspeakers within the open space is selected based on the desiredvariable height above the open space floor.
 4. The system of claim 1,wherein the noise masking sound audio file comprises a random noisecomprising a frequency range of 160-8000 Hz and a natural soundcomprising a frequency range of 120-10000 Hz.
 5. The system of claim 1,wherein the display device is arranged to be visible from any locationwithin the open space.
 6. The system of claim 1, further comprising awater element system generating a sound of flowing water.
 7. The systemof claim 1, further comprising a plurality of microphones, wherein eachmicrophone of the plurality of microphones is associated with a balancedmode radiator loudspeaker of the plurality of balanced mode radiatorloudspeakers.
 8. The system of claim 7, wherein the one or moreapplication programs include instructions to select the noise maskingsound audio file from the one or more selectable noise masking soundaudio files and the video file from the one or more selectable videofiles utilizing a microphone output data from the plurality ofmicrophones.
 9. The system of claim 1, wherein the one or moreselectable noise masking sound audio files comprises a nature associatedsound and the one or more selectable video files comprises a natureassociated visual.
 10. The system of claim 9, wherein the natureassociated sound comprises a water sound and the nature associatedvisual comprises a water visual.
 11. The system of claim 9, wherein thenature associated sound comprises a beach sound and the natureassociated visual comprises a beach visual.
 12. The system of claim 9,wherein the nature associated sound comprises a forest sound and thenature associated visual comprises a forest visual.
 13. A method formasking open space noise comprising: outputting a noise masking soundfrom a plurality of balanced mode radiator loudspeakers distributed in adown-fire direction above an open space, the plurality of balanced moderadiator loudspeakers disposed at a desired height above an open spacefloor and wherein a total number of balanced mode radiator loudspeakerswithin the open space is selected based on the desired height above theopen space floor; and displaying a visual corresponding to the noisemasking sound.
 14. The method of claim 13, wherein the noise maskingsound comprises a random noise comprising a frequency range of 160-8000Hz and a natural sound comprising a frequency range of 120-10000 Hz. 15.The method of claim 13, further comprising: receiving a microphone datafrom a plurality of microphones disposed in the open space; andadjusting the noise masking sound utilizing the microphone data.
 16. Themethod of claim 13, wherein displaying the visual corresponding to thenoise masking sound comprises displaying a nature visual on a videodisplay device.
 17. The method of claim 13, wherein the noise maskingsound comprises a water sound and displaying the visual corresponding tothe noise masking sound comprises displaying a water element system, thewater element system generating a sound of flowing water.
 18. The methodof claim 17, wherein the water element system generating the sound offlowing water comprises a floor-to-ceiling waterfall.
 19. The method ofclaim 13, wherein the noise masking sound comprises a nature associatedsound and the visual comprises a nature associated visual.
 20. A systemfor masking open space noise comprising: a plurality of balanced moderadiator loudspeakers arranged above an open space to output a noisemasking sound in a down-fire direction, each balanced mode radiatorloudspeaker of the plurality of balanced mode radiator loudspeakerscomprising a voice coil, a diaphragm, and one or more mass objectscoupled to the diaphragm; a plurality of microphones; and one or morecomputing devices comprising: one or more processors; one or morememories storing one or more application programs executable by the oneor more processors, the one or more application programs comprisinginstructions to receive a microphone data from at least one of theplurality of microphones and adjust the noise masking sound output atone or more of the plurality of balanced mode radiator loudspeakers. 21.The system of claim 20, wherein the plurality of balanced mode radiatorloudspeakers are disposed at a desired variable height above an openspace floor.
 22. The system of claim 21, wherein the desired variableheight is determined by an extension segment having a first end coupledto a ceiling and a second end coupled to a balanced mode radiatorloudspeaker.
 23. The system of claim 21, wherein a total number ofbalanced mode radiator loudspeakers within the open space is selectedbased on the desired variable height above the open space floor.
 24. Thesystem of claim 20, wherein the microphone data comprises noise levelmeasurements, noise frequency data, or voice activity detection datadetermined from sound detected at the plurality of microphones.
 25. Thesystem of claim 20, wherein the noise masking sound output comprises arandom noise comprising a frequency range of 160-8000 Hz and a naturalsound comprising a frequency range of 120-10000 Hz.
 26. The system ofclaim 20, further comprising a display device outputting a visualmatching the noise masking sound.
 27. The system of claim 26, whereinthe visual comprises a water visual, a beach visual, or a forest visual.